NFS: fix umount of pnfs filesystems

Unmounting a pnfs filesystem hangs using filelayout and possibly others.
This fixes the use of the rcu protected node by making use of a new 'tmpnode'
for the temporary purge list. Also, the spinlock shouldn't be held when calling
synchronize_rcu().

Signed-off-by: Weston Andros Adamson <dros@netapp.com>
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 12 insertions, 5 deletions

diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index 48d0a8e4d062..96bf4e6f45be 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -186,6 +186,7 @@ int pnfs_ld_read_done(struct nfs_read_data *);
 /* pnfs_dev.c */
 struct nfs4_deviceid_node {
         struct hlist_node               node;
+        struct hlist_node               tmpnode;
         const struct pnfs_layoutdriver_type *ld;
         const struct nfs_client         *nfs_client;
         struct nfs4_deviceid            deviceid;
diff --git a/fs/nfs/pnfs_dev.c b/fs/nfs/pnfs_dev.c
index c65e133ce9c0..5944d4b369a2 100644
--- a/fs/nfs/pnfs_dev.c
+++ b/fs/nfs/pnfs_dev.c
@@ -174,6 +174,7 @@ nfs4_init_deviceid_node(struct nfs4_deviceid_node *d,
                         const struct nfs4_deviceid *id)
 {
         INIT_HLIST_NODE(&d->node);
+        INIT_HLIST_NODE(&d->tmpnode);
         d->ld = ld;
         d->nfs_client = nfs_client;
         d->deviceid = *id;
@@ -238,24 +239,29 @@ static void
 _deviceid_purge_client(const struct nfs_client *clp, long hash)
 {
         struct nfs4_deviceid_node *d;
-        struct hlist_node *n, *next;
+        struct hlist_node *n;
         HLIST_HEAD(tmp);
 
+        spin_lock(&nfs4_deviceid_lock);
         rcu_read_lock();
         hlist_for_each_entry_rcu(d, n, &nfs4_deviceid_cache[hash], node)
                 if (d->nfs_client == clp && atomic_read(&d->ref)) {
                         hlist_del_init_rcu(&d->node);
-                        hlist_add_head(&d->node, &tmp);
+                        hlist_add_head(&d->tmpnode, &tmp);
                 }
         rcu_read_unlock();
+        spin_unlock(&nfs4_deviceid_lock);
 
         if (hlist_empty(&tmp))
                 return;
 
         synchronize_rcu();
-        hlist_for_each_entry_safe(d, n, next, &tmp, node)
+        while (!hlist_empty(&tmp)) {
+                d = hlist_entry(tmp.first, struct nfs4_deviceid_node, tmpnode);
+                hlist_del(&d->tmpnode);
                 if (atomic_dec_and_test(&d->ref))
                         d->ld->free_deviceid_node(d);
+        }
 }
 
 void
@@ -263,8 +269,8 @@ nfs4_deviceid_purge_client(const struct nfs_client *clp)
 {
         long h;
 
-        spin_lock(&nfs4_deviceid_lock);
+        if (!(clp->cl_exchange_flags & EXCHGID4_FLAG_USE_PNFS_MDS))
+                return;
         for (h = 0; h < NFS4_DEVICE_ID_HASH_SIZE; h++)
                 _deviceid_purge_client(clp, h);
-        spin_unlock(&nfs4_deviceid_lock);
 }